Method of making layered armors



Mal'h 27, 1945 P. scHwARzKOPF 2,372,607

METHOD OF MAKING LAYERED ARMORS Filed Nov. 25, 1940 Patented Mar. $7, 1945 2,372.60? Mn'rnop or MAKING ternana amiens raul Schwarzkopf, Yonkers, N. y., assigner to American Electro Metal Corporation, FLY., a corporation oi Maryland Yonkers,

Application November 23, 194i?, Serial No. 366,@i8

Claims.

This invention relates to the method of making an armor composed of two or more layers of 4 dierent compositions, in particular of alternating layers of diierent structure and composition.

It has been suggested to combine a plurality of armor plates or sheets into a composite body, and also to differentiate those plates or sheets as to their composition. It has further been suggested to combine plates or sheets of armor steel f with resilient or soit means in order to more rresilient-ly receive the impinging projectile.

nose and periphery oi the projectile are changed while the projectile penetrates into the armor, so as to increase resistance against further penetration.

lt is another object of the invention to compose the armor of layers or strata/of dierent kinds or types oi material one of which is substantially tough and hard, while the other is capable of chipping, cutting and/or grinding the nose and the periphery oi' the penetrating projectile.

It is still a further object of the invention to compose an armor of several alternate and bonded layers or strata of different kind or type, one kind or type of these layers or strata consisting of a hard and relatively tough material capable of cutting, chipping and/or grinding the penetrating nose and periphery of the impinging and penetrating projectile.

It is still another object of the invention to compose the armor of layers or strata of two forming the surface and shape of the penetrating projectile. f

Still 'another object of the invention consists in. manufacturing a composite armor of several alternating bonded layers or strata of 'basically dierent composition and structure, one kind of those layers or strata consisting of armor steel of any desired composition, the other of a hard and tough material capable ci chipping, cutting and/or grinding the mantle oi the projectile, and to bond the layers of the latter material with those of the armor steel during manufacture of the former.

lt is a further object of the invention to manufacture a layered armor from plates or sheets of armor steel or other suitably tough and hard material, and a hard metal composition comprised of hard carbide, nitride and/or boride particles cemented by a tough and substantially metallic binder, the layers of hard metal being completed and simultaneously vbonded with the preformed layers of armor steel or other hard and tough material.

A specific object oi the invention is a layered armor composed of plates or sheets oi armor steel and intermediary layers of hard metal of ythe type referred to, the hard metal being of substantially equal or lower specific weight than armor steel, and to manufacture the armor so as to eEect a vhrm bond between the hard metal layers and the be more clearly understood when the specication diierent kinds or types of material one being primarily tough and hard and capable of resisting the penetration of the projectile to predetermined extent, while the other.` is primarily capable of deforming the shape of the impnging and penetrating projectile.

A still further object of the invention consists in an armor composed of bonded layers or strataof diierent types, one type consisting in a cast and thereafter thermally and/or mechanically treated material and the other type in a sintered hard and tough material capable of chipping, cutting, grinding, rougliening or otherwise deproceeds with reference to the drawing in which Fig. 1 shows a cross section through a piece of an armor according to the invention, Figs. 2 and 3 more schematically and in exaggeration the effect of the new armor upon the nose of a penetrating projectile, Fig. 4 more schematically a mode of manufacturing a composite armor in a continuous process, Fig. 5 more schematically a process o! preparing a sheet or plate of armor steel for subsequent handling in a. process according to the invention, Figs. 6 and 7 more schematically two steps of a process in which armor steel plates are combined with an intermediary layer ofhard metal. Figs. 8 and 9 more schematically another manufacture oi.'` an armor composed of plates and an intermediary hard metal layer, and Fig. 10 more schematically amodication of the latter process'applied to the manufacture o1' bent armors.

Referring to Fig. 1 the armor consists of a number of armor plates, sheets or strata. I0, Il and I2 spaced from each other, the spaces be-v tween them being occupied by layers or strata of cemented hard metal I3, I 4 bonded with the adjacent plates. Assuming that a projectile I5 arrives in the direction of arrow I6 and rotates in the direction .of arrow 'I9 around its axis, the projectile will rst percuss plate I0 and thereafter penetrate into layer I3. While the nose of the projectile digs into layer I3, the hard parti- I in Fig. 3.

It will be appreciated that by the percussion of plate I0 the speed of the projectile is somewhat decreased and some kinetic energy stored therein consumed.` By working its way through the cemented hard metal layer I3, the speed and kinetic energy of the projectile is further reduced and in addition thereto another'part of its kinetic energy consumed by the deforming, cutting, chipping or grinding action of the hard metal upon the surface of the noseof the projectile.

Simultaneously the aptitude of the projectile to further penetrate into and percuss the armor is considerably reduced by that deformation of its nose and roughening of its surface.

It is well known that the mantles of projectiles are made as hard and smooth as possible, in order tofacilitate penetration of an armor. Sometimes metals of relatively low melting point, such as cadmium, are used as coating or` cover\ of the mantle; when the armor is hit, thev metal isA instantaneously heated to a high degree, it melts and acts like a liquid lubricant on the mantle, while the projectile penetrates into the armor. The purpose of thelcemented hard metal layer or layers according to the invention is primarily to deprive the penerating projectile of its smoothness, as well as of its shape proper for further penetration. It also serves to abrade any lubricant material from the mantle. Furthermore, any deformation, roughening or abrading action consumes part of the kinetic energy of the projectile, and all these factors combined result in the reduction of.the penetrating power of the:

projectile t0 a considerably ,higher degree, as it would be the case of instead of a cemented hard metal layer, according to the invention, a plate or layer of armor steel of equal thickness an weight were provided.

Reverting to 1, it will-now be understood that penetrating of armor plate II lis more diicult for the projectile than of the first armor plate I0; the projectile is somewhat deformed and roughened, and its lubricant abraded.

Due to this deformation of the nose and consid.. erable loss of kinetic energy in passing the cemented hard metal layer I3, plate Il will be ca*- pable of' more effectively resisting penetration by the projectile and t0 again reduce the speed or kinetic energy stillstored in the'projectile.

Upon penetration into the second cemented hard metal layer I4, another deforming or roughening action is exerted upon the nose of the projectile; due to its considerably reducedspeed of the projectile penetrates cemented hard metal layer I6 more slowly andl can be more effectively worked upon by the cemented hard metal inthe sense described above. This Iresults in an additional and more considerable deformation of its nose, as shown somewhat in exaggeration in Fig. 3.

Depending upon the size and energy stored in the projectile, it will be sufcient to provide three layers of armor steel with two intermediary layers of cemented hard metal, as shown in Fig. 1, to stop the projectile in or on the armor plate I2. It will be further appreciated that according to the size of and stored energy in a projectile intended to be resisted by an armor, the number of armor plates and intermediary cemented hard metal layers can be increased to the effect described above, or reduced to one cemented hard metal layer or stratum backed byone layer of steel; sandwiching of a cementedl hard metal layer or stratum between two layers or strata of steel is however preferred.

As tothe composition of the armor steel plates or sheets, in general any known composition can be used, such as hard and tough alloy steel e. g. chromium steel, nickelI steel, manganese-nickel steel, molybdenum-nickel-steel, manganese steel,

'phosphorus steel; however,v1ow carbon steel preferably relaxed and vnot springy, such as steel known as U. S. Steel COR-TEN," hot rolled and relaxed low carbon steel, and not or only slightly their bonding with armor steel of known composition is impossible without melting and mining at least the shape of the latter. As such sintered hard metal compositions, those of carbides, ni

' trides or borides of tungsten, molybdenum, chromium, tantalum, niobium, vanadium, titanium, zirconiumand boron are usable. Due to their low specific weight, extreme hardness and availability in this country, carbide, nitride or boride of titanium are preferred. Any suitable mixtures of any two or more of the compounds referred to and'preferably-combined into compounds or solid solutions of even greater hardness. can be used. As a binderfor the hard particles tough materials, such as cobalt, nickel andviron vare`preierred. however for reasons to be set forth later on, also alloys can be applied using iron-as a base and cobalt, nickel.' copper and aluminum as additions; there may further be used an alloy such as of copper and nickel, copper and cobalt, etc.l All these binders or cementing materials have considerably lower melting temperatures than the carbides, borides or nitrides. r I'he latter are first to be prepared f ronrthe chosen metal basis in well known processes and thereafter to be comminuted to desired particle size. In contradistinction to hard metals as known and used for tool materials, the invention is not so much concerned with extremely 'fine' andvuniform particle sizes; though particle sizes averaging from 5 to 30 microns may be used to advantage for light armors andthin hard metal strata., larger particle sizes, up to 100 micron and more are preferred for heavier armors or thicker hard metal layers.V

It will be appreciated that with the invention ltively little kinetic energy.

no eect comparable with normal machining of a work is attempted, the latter resulting in accurately shaping the work and smoothing and equalizing its surface. According to the invention, the smth surface and given shape of theto as fine as possible grinding and vconsequently rounding on of hard particles to be used in tool materials.

While the binder in tool materials is to give toughness to the tool so that it can be used for a long period of time without losing its shape. and can sustain a great many shocks during machining, with the invention conditions similar to those prevailing with tool materials do not exist. The

binder serves to/cementing, i. e. firmly hold the particles in their position and to connect the adjacent armor plates. When the cemented hard metal comes into action, i. e. a projectile penetrates into it, this only occurs once and is to the effectof at least partly destroying the layer. Hence no views as to a long life time and sustaining a great many consecutive shocks apply to the binder.

Under the impact of tle projectile, the hard metal layer will crack locally, and the great mass of hard particles contained therein will act upon the projectile, whether they are still bonded together or not. If firmly held in place, they will cut into and tear the surface of the mantle; if they become loose, they will act like blasts of extremely hard sand or abrading powder upon the nose. No time is given to any locally loosened parts to fall ofi their backing plate or sheet, or toll/dodge aside.

The armor steel plates backing each hard metal layer will assist in keeping the hard metal, still bonded or locally cracked, in its place, and thus operate not only as individual obstacles to the penetration of the projectile when it reaches that plate, but in addition thereto as an effective backing of the hard metal in front of it.

This cognizance of the invention is of extreme importance for facilitating manufacture of an armor according to the invention.

It has been mentioned above that hard particle sizes of about to 30 lmicrons are advantageous for relatively .light and thin armors. It is understood that relatively light armors alord protection only against relatively light projecticles having little masswhich can store relaa great many of the extremely smallhard particles will be hit simultaneously by the nose of the projectile when it impinges the armor. `The ne hard particles will not crack under the impact anymore. The metal binder cementing them cannot be softened by the relatively small amount of heat developed by the impact, and firmly holds the hard particles hlt. Thus the nose of the impinging projectile will be deformed and flattened by the hard particles hit; if the nose is somewhat elastic, the projectile will be repelled like an elastic ball, and if the nose is not elastic, the projectile will be stopped It is A obvious that and fall to the ground. In any event such light projectiles cannot penetrate the cemented hard metal layer or detrimentally indent it, and consequently the layer and its backing can be made relatively thin and correspondingly light in weight.

As a binder any material as mentioned above can be used. Soft pure iron (ferrite) is of particular utility for reasons to be set forth later on.

In, general the cementing binder is also powdered and intimately admixed with powdery hard particles to form the initialmixture from which the layer -is to be made. The size of the particles of the binder should advantageously be as small as possible in order to facilitate production. Sizes from 3 to 30 microns are therefore preferred, though larger ones may be used.

As to the ratio of hard particles and binder, the specific weight or volume of the former must be considered. The smaller the specic weight, the smaller should .be in general the relative amount by weight of those hard particles. While with tungsten carbide which is of a specilc weight of 15.5, amounts of a binder of between 9% to 15% (or higher) are preferred, with tiiron group metals, the relative amount of the binder should be accordingly reduced.

In general therefore, for hard particles and binder materials of the kind recited above, a ratio of .from 91% to 60% by weight of hard particles and from 9% to t220% binder may be given, without limiting however` the invention to any particular ratio or range.

Referring to Fig. 4, the manufacture of an armor, consisting of sheets of e. g. relaxed low carbon armor steel of a thickness of about 1/25" Yto l/l" and intermediary layers of hard metalof the same or greater thickness shall be described by way of exemplication. From a supply roll la of steel sheathing, a sheet il is drawn o by means of rollers la, i9, pressed against the sheet and driven in the direction of the arrows with predetermined and preferably adjustable speed. The sheet travels in the direction of arrow 22 into a unit 26 (indicated in dotted lines) comprising a hopper 2li filled with a powdery initial mixture and provided with Ia pro,- peller or other means for depositing predetermined and preferably adjustable amounts of the initial powdery mixture during a `unit of time, in a layer of desired thickness onto sheet ll. Roller 23 is pressed from above upon the exposed surface of layer 2l and backing roller 2li from below onto the lower surface of sheet Il. Thereby the hard metal powder is spread uniformly over and pressed into the sheet. Depending upon the pressure exerted by rollers 23, 24, more or less compacting of the layer and superficialV mechanical uniting with sheet l1 can be obtained even in the cold. Pressures of the order of 15` tons p. s. i. generally .suffice if finest powders of cobalt, nickel orferrite form the binder.

'Rollers 23, 24 can either be heated or separate heating means lcan be arranged vbehind them. If the rollers were heated forinstance by an electrical resistor (not shown), placed inside them or their shafts, somecompacting of the layer and its superficial bondingk with the sheet can be obtained by pressure on the rollers of an order of 2 to 5 tons p; s. i. Such compacting will also be arrived at while the layer and sheet pass furnace 25. Temperatures from 500"V to '700 C. should not be exceeded in order to prevent undesirable oxidation and to avoid needless waste of heat; if higher temperatures are desired to be applied in order to effect presintering, or if for other reasons advisable, a protective Aatmosphere can be used in furnace and along the following path of the sheet and layer thereon. If desired, any number of units similar to unit 25 can be arranged behind it; vone such unit 26' is indicated in dotted lines. In those units, ar ranged in series, either exactly the same conditions can prevail, or the pressure exerted by rollers 23, 24 can be raised from unit to unit, and/o1' the temperature of furnace 25 raised from unit to unit to the desired maximum. Such series arrangementof units is preferred if'layers` of greater thickness are to be applied.

Sheet II provided r(with layer l2| of desired thickness andA preferably compacted, travels now under supply roll 21 of a sheet of armor steel of the same or different composition, same or different thickness as sheet n A sheety 28 is wound'off supply roll 21 ,by rollers 29, l3l) driven in the direction shown by arrows and pressed from above and below against the upper side of sheet 28 andthe lower side of sheet I1, respectively. The pressure should be sufficently high" (a few tons p. s. i.) in order to firmly set sheet 28 upon layer2l. The two sheets I1 and 28 with intermediary layer 2| now travel through a furnace comprising a heating chamber and a cooling chamber 33. The heating chamber is formed by a preferably tubular refractory 32 inwhich electrical resistance heat. ers 3| are inserted. The latter may consist .ofV

suitable material of suiiiciently high melting point such as tungsten, molybdenum, etc., as well `known inthe art. By adjusting the heating current any desired temperature can be obtained Within chamber 30. Any other type of iurnace,

such as `of the induction type, can be used.

The temperature in chamber 38 should be such that the -initial hard metal mixture is sintered.

Depending upon the nature of the binder, the

kept between about 1000 to 1350 C., and in any way substantially below the melting point of the armor steel sheet used, and above about 900 C. 'During'sin'tering of the binder, also diffusion or coalescing between the binder and'adjacent surface layers of the sheets l1 and 28 occurs..

securing a firm bond between the binder and thereby the hard metal layer 2| and those sheets.

During the travel of the combined sheets and layer now forming a unit throughchamber 30 sintering iscomplete'd, vand cooling starts whilethey travel through chamber 33. Cooling is effected by a cooling jacket 34 ,passed by a suitable cooling or refrigerating medium. Jacket 33 may besubdivided in order to' exert a staggered cooling action according to a desired cooling curve upon the sintered unit passing it. By suitl able vdimensioning the length of chamber 33 with Arespect to the speed of travel of the unit through fast or slow cooling, or rst fast and then slow cooling, or vice versa, caneasily be effected.

yIt should be understood thats-he process as illustrated in Fig. 4 can be multiplied in any desired way. The temperature in a heating chamber 30 can be kept below 1000 C., thus eiecting i only a preliminary bond -between sheet 28 and the layer 2| compacted or presintered upon sheet and the unit so obtained may be pushed into another one or into a series of units 26 in which another powdery layer is deposited upon sheet 28 and compacted'` or presintered thereon. Thereafter another sheet of armor steel may be positioned upon that second upper layer in the them.

It is vevident however that sheets |1, 28 with intermediary nally sintered layer 2| can be introduced in another process in which another layer of hard metal and another sheet is added to it in a similar process, and these processes can be multiplied until iinallyran Iarmor-consisting of a desired number of armor steel sheets and in termediary sintered layers of hard metal sandwiched between and bonded with them is obtained.

Itis also evident that instead'of heating rollers '23, 24 -or rollers 29, 30, and instead' of or in addition'to furnaces 25 any-other heating means can be used, such as rows of r'acetylene-oxygen burners arranged above and 4across the exposed surface of layer 2|, as indicated in-dotted lines at 52 and y53. The flame of those burners has to be regulated so as to effect the desired heating and may be of oxidising, de'oxidising, or neutral character in order to .either-oxidise e. g. superi fiuous carbon, if present, or to remove undesired oxide lms if formed on the powdery particles of the layer, or not to atleet them' at all.

In order to preventoxidation, or to`deoxidise l the exposed surfaces of sheets l1, 28, a suitable `sintering temperature in chamber 30 should be gas can be led through chambers 30 and 33. To this effect a hood 35 is provided at the entrance of chamber 38 closing as near-as possible to the sheets, and a suitable gas, such as hydrogen, carbon monoxide or dioxide, hydrocarbons, cracked gases, etc. is introduced through tube 54 and released at the other end 58 of the furnace where they may be burned oil'.

Assuming that powdery pure iron (ferrite) is used as a binder, its melting temperature is about 1530" to 15504 C., and its presintering. temperature is therefore about 1100 C.; it starts to become plastic at 'about 100 lower, so thatwithin y the unit. 23 a temperature up to 900'? C. or somewhat higher-'can be applied if presintering is desired. In chamber 30 a temperaturevabove 1100"- C., but vlNlollW'1300 1901350 C. which iS the melting point of low carbon steel, should be applied. l*

At such temperatures complete sintering'of the ferritic iron can 'only be obtained if the. ferrite powder is extremely tine and the period of sintering extendedto between 2 and 41hours. ever, complete sintering is not-a. condition of the invention. Even a still somewhat porous hard 'l vmetal will suit the purpose of the invention, since the ferrite'combines with the steel at considerably lower temperatures'and secures a bond be-- tween the binder and the armor steel sheets firm How- I enough lfor mounting the plate on stationary or mobile objects.' auch as tanks `or aircraft.

As pointed out above. no substantial mechanical force vis acting upon the hard metal layer comparablev in any respect with the strain exerted upon tool materials in machining a work. -At the momentof impact of the projectile however the bond ail'orded also by a more'or less porous binder will suiice.

If nickel is used as a binder. presinteringteml@ peratures of aboutv 1000" C. Vare sumcient, and\ nickel plasties suillciently and below 900 C. so as to obtain a compact of the hard -metal layer.

High sinteringtempertureof nickel is about 1300" Similar views apply to the use of cobalt, the

presintering and sintering temperatures of which are only a few Adegrees higher than those of nickel. f

In connection with the above it should also be considered 'that the presintering and sintering temperature of the. -metals dealt with are somewhat lowered by the presence of the interspersed hard particles, thus securingtheeflect of the invention. However, if alloy steels of particularly low melting point are used for the armor steel plates or sheets, composite binders can be used, as mentioned above, or stellite.

' The sintering temperature of ferritic iron can be reduced by about 100 by the admixture of about copper, and a higher percentage of copper further reduces those temperatures. Diffusion 4temperatures of copperand iron can be found even below 1100 C., and thus in chamber the copper admixed to the binder will diiuse into the armor steel sheets eand thereby assist in creating a rm bond.

In a similar way, by admixture of 20% aluminum to pure iron, its sintering temperature 'can be reduced by about 100 C.. and the aluminum diffuses and bonds together the iron particles as well as the iron with the armor steel at far lower temperatures.' about 820 C., if 20% aluminum is admixed, and thus assists in creating a bond between the hard metal layer and the steel sheets even during presintering. the temperatures of which can be kept accordingly low.

If nickel is used as a binder, remarkable reductions in the sintering temperatures can be attained by the addition of chromium. An admixture of chromium reduces the sintering temperature by at least C. and an admixture of 43% chromium lowers the presintering and high sintering temperatures of nickel by more than 150 C. Higher chromium admixtures still mixing copper.

It should be understood that the above are only a few examples for illustrating the possibilities and advantages of the invention and its utter diiferenc'e from the uses ordinary hard metal .can be -put to. a

In order to increase the bond between the.

binder and the sheet, the surface of the latter to be contacted by the hard metal layer can. be

tates permeaton of the plastiiled binder during sintering. In addition, the enlarged surface greatly assists diffusion. Portions of the binder penetrating the pores are quasi mechanically a hopper 5l filled with the desired nest powdery anchored in it and the strength of the bond is additionally increased. 'Ihe irregular valleys and ridges obtained by mechanical roughening also serve to increase the surface for diffusion and mechanically bonding the plastied and pressed on binder, cementing the hard. particles. Another way of assisting the bond consists in plating the armor` steel sheet with a suitable metal,`such as iron, sponge iron, copper, 'nickel cobalt, Monel metal, alloys of copperI iron, copper cobalt, .copper nickel, iron nickel, nickel vanadium, copper vanadium, etc. To this eiect an arrangement as illustrated in Fig. 5 can be used.

Here again a. sheet or lplate lil-can be moved by means of driven feeding rollers 55, 55. below metal or alloy as exemplied above and driven in adjustable quantities by propeller 58 through the .discharge opening of hopper 51, so that an ex- -tremely thin layer 59 isdeposited and spread over sheet or plate 54. The sheet is moved through a heating chamber 60 and cooling champer 8l ofa furnace 62 provided with cooling jacket 53, thestructure of which is substantially the same as of heating chamber 30 and cooling chamber 33 of Fig. 4. Again a hood 64 can bev provided into which protective gas is led through tube and released at 66. The temperature within the chamber 60 should be kept below about 700 to 900 C., but above about 450 to 500 C., the same way as in the compactng or presin,

-and used in the process illustrated in Fig. 5.

'I'he 'thus or in another way well known in the art plated or coated sheet or plate is then used in any process herein described, e. g. as sheets Il, 28 or plates 38, 44, 61, 8|, the plated or coated surface to be on the side where the hard metal layer or stratum is tobe applied. If a sheet or plate is sandwiched between two hard metal layers the plate or sheet is to be plated or coated on both sides.

In order to manufacture an armor of stiff plates, a. process as illustrated in Figs. v6 and 7 can be used. Plate- 67 is positioned on supporting rollers 58 and driven by another roller 69 in the direction of arrow 1B. The plate passes under a hopper ll provided with propeller 'l2 and lled with the powdery initial hard metal mixture. A.

layer of the powdery mixture is deposited on the plate and preferably heated pressure rollers 13, 18 compact the layer on and onto the plate. The

whole is than passed through fiu'nace chamber 1t and cooling cr 'i5 the structures of which need not be explained in detail any more. Protective gas is led in through tube 10 and hood 1l and released at l0. The temperature within chamber 14 should be between 500 to about 900 C. in order to further compact or presinter or frit the hard metal layer and bond it to some ex.

tent to plate 61. Pressure may be exerted upon it while still hot, but below about 500 C., by presl sure rollers 19, 80.

Upon this unit another armor steel plate 0l time, the same way and to the same eilect as described with reference to Fig. 4, and in cooling chamber 85. which may be subdivided for the purpose set forth above, any desired annealing or other heat treatment of the steel plates can be effected. The armor leaves the'iurnace in this case the same way as in the continuous process described above at a temperature below 900 C.

and preferably below 500 C. It should be understood that any number of plates and hard metal layers can be combined in the way described. Any hard metal layer deposited upon a plate should be heat treated at or below about 700 to 900 C. for compacting and presintering, if desired, another plate positioned and pressed thereon, etc., and the unit consisting of the desired number of layers and plates then nally compressed and sintered.

If the sheet-like armor obtained in a process as illustrated in IFig. 4, or the plate-like armor illustrated with refernce to Figs. 6 and '1, is to be cut to shape thereafter, this should be done while it is still hot, preferably immediately after it leaves the last sintering furnace. i

Another way of manufacturing armors comprising stiff plates is illustrated in Figs. 8 and 9.

A die 31 is used, provided with recesses 48, and

armor plate 38 is positioned in the die. 'I'hereafter a hopper 40 containing a powdery initial hard metal mixture 43 and provided with a propeller 42 for the purpose set forth above is moved to the right in the direction of the double arrow 4I over the die. While above the opening of the die, propeller 42 is rotated and a layer of hard metal deposited upon plate 38 in the die. The hopper may be moved any desired num ber of times back and forth over the opening of the die, until a number of powdery layers is deposited thereon giving the desired thickness of the sintered hard metal layer, considering inthis case the same way as in those described above the shrinkage during sintering (or presintering). Thereupon another plate 48 is positioned in the die, pressure plate 45 is lowered in the direction of the arrow in Fig. 8. the whole is cornpressed (25 to 100 tons p. s. i.) and in this example heated by induction heating to sintering temperatures above 900 C. and preferably between about 1000 to below 1350 C. Coils i6 are provided for this eect. Heating and pressing may be eected simultaneously or alternatively and repeatedly. Pressure member 85 may also be used like a drop hammer.

Before plate M is inserted, and while the die is still open, plate 30 and layer 30 deposited thereon may be heated to a temperature below '100 to 900 C. in order' to eiIect compacting or presinterlng of the powdery initial hard metal layer, and some shrinking and degasiilcation. 'Ihe sintered armor is removed by angular instruments inserted through recesses 48.

Here again any number of plates and hard.

metal layers can be combined in the way described above. If -a curved armor is to be produced, a die 80, Fig. 10, can-be used, upon which the precurved armor plate 49 is positioned. Subsequently a powdery initial hard metal layer 5l is deposited. upon plate I9, principally in the same way as described with reference to Fig. 8. However, in this case some binder (about 1 to 6% by weight), suchas water, dextrine, glycerine, glucose should be admixed to the powder in order to render it plastic. Instead of using a propeller in hopper 40, a piston then should be used which is pressed downwardly at predetermined speed,

binder and simultaneously s uiilciently compact or presinter the layer 5I on and'onto plate 49, to degasify it and to effect considerable shrinking. Thereupon plate 50 is inserted in the die and processed and nally sintered in the way' described with reference to Fig. 8, or any number of additional hard metal layers and plates applied and the Whole then nally pressed and sintered in the way-described above.

It should be understood that the invention is not limited to any preferred features described herei'nbefore, but to be derived in its broadest aspects from the appended claims.

\ What I claim is:

'1. A process of manufacturing a layered armor composed ofa number, two as a minimum, of layers.v or strata of difi'erent type material, a first type being ferrous, tough and hard and including in its manufacture a casting step, while the second type of material consistsof a slntered hard metal composition obtained by sintering an initial mixture of hard particles selected from carbides, nitrides and borides of at least one element selected from the group consisting of tungsten, molybdenum, chromium, tantalum, niobium, vanadium, titanium, zirconium and boron, and a' powdery cementing metal of lower melting point than said particles, said cementing metal always including an appreciable amount of iron group metal, vcomprising the steps of depositing at least one layer of said initial mixture upon said i'lrst type layer, compacting said deposited layer upon a completed layer of the iirst type, and finally heating said layers to temperatures between about 900 to below 1350 C. until said mixture is iinally sintered and essentially simultaneously firmly bonded with said first type layer,

2. In a process as claimed in claim l, the step of heating the deposited layer on said completed first type layer to below about 900 C. before subjecting them to nal sintering.

3. In a process as described in claim 1, the step of presinterlng said deposited layer lupon said completed rst type layer, before final sintering.

4. In a process as described in claim 1, heating the deposited layer to a temperature below about about 1% to 6% of a binder exemplified by or- '700 to 900 C. and compressing ,it previous to final sintering. y

5. In a process as described in claim 1, the step of roughening the surface of saidcompleted rst type layer to be bonded with said second type layer before applying the latter.

6. In a process as described in claim 1, the step of coating a surface of said completed first type layer to, be bonded with said second type layer, with a bonding metal composition essentially consisting of an appreciable amount of chromium and a balance selected from iron group metal, before applying the said second type layer.

7. A process of manufacturing a layered armor composed of, a number, two as a minimum, of layers or strata of different type material, a rst type being ferrous, tough and hard and including in its manufacture a casting step, while the second type of material consists of a sintered hard metal composition obtained by sintering an initial mixture of hard particles selected from carbides, nitrides and borides of at least one element selected from the group consisting of tungsten, molybdenum, chromium, tantalum, nlobiers into a heating device for nally sintering said J second type layer upon said first type layer.

8. In a process as described in claim 1, the Step of shaping said layers united by final sintering while still hot at temperatures exemplified by about o to/beiow 900 C.

i9. A. process of manufacturing a layered armor composedof a number, two as a minimum, of layers or starta of different type material, a rst type being ferrous, tough and hard and including in its manufacture a casting step, while the second type of material consists of a sintered hard metal composition obtained by sintering an initial mixture of hard particles selected from carbides, nitrides and borides of at least one element selected from the group consisting of tiingsten, molybdenum, chromium, tantalum, njkiobium, vanadium, titanium, zirconium and boron,

and a powdery cementing metal of lower melting point than said particles, said cementing metal always including an appreciable amount of iron group metal, comprising the steps of placing said completed first type layer in a die, depositing thereon a layer of said initial mixture, compacting said deposited layer upon said i-lrst type layer, and finally heating said layers to temperatures between about 900 to about 1350 C. until said second vtype layer is finally sintered and rmly bonded with said first type layer.

10. In a 'process as described in claim 9, the step of placing previous to final sintering a completed first type layer upon said second type layer deposited on the completed first type layer previously placed in the die.

11. In a process as described in claim 9, placing a completed rst type layer of other than straight shape into a die, and depositing thereon at least one layer of said initial mixture admixed with garlic and volatile binders.

12. A process of manufacturing a layered armor composed of a number, two as a minimum, of layers or strata of different type material, a first type being ferrous, tough and hard and including in its manufacture a casting step, while the second type of material consists of a sintered hard metal composition obtained by sintering an initial mixture of hard particles selected from carbides, nitrides andborides of at least one element selected from the group consisting of tungsten, molybdenum, chromium, tantalum, niobium, vanadium, titanium, zirconium and boron, and a powdery cementing metal of lower melting point than said particles, said cementing metal always including an appreciable amount of iron group metal, comprising the steps of continuously feeding a completed rst type layer under means for depositing thereon a layer of an initial mixture for said second type layer and depositing said second type layer on said completed first type layer, feeding said layers into means for compacting'said deposited layer upon said first type layer, thereafter successively passing said layers through heating zones of different degrees of temperature, in the rst of which said deposited second type layer is heated to a temperature below about 700 to 900 C. and in the last of which said deposited layer is heated to nal sintering temperature and thereby nal-v ly sintered and also firmly bonded with said rst type layer.

13. A process of manufacturing a layered armor composed of a number, two as a minimum, of layers or strata of different type material, a first type being ferrous, tough and hard and including in its manufacture a casting step, while the second type of material consists of a sintered hard metal composition obtained by sintering an initial mixture of hard particles selected from carbides, nitrides and borides of at least one'element selected from the group consisting of tungsten, molybdenum, chromium, tantalum, niobium, vanadium, titanium, zirconium and boron, and a powdery cementing metal of lower melting point that said particles, said cementing metal always including an appreciableA amount of iron group metal, comprising the steps of continuously feeding a completed first type layer under means for depositing thereon a layer of an initial mixture for said second type layer and depositing said second type layer on said completed first type layer, passing said layers through means for comrpacting said deposited layer upon said rst type 'first type being ferrous, tough and hard and including in its manufacture a casting step, While .the second type of material consists of a sintered hard metal composition obtained'by sintering an initial mixture of hard particles selected from carbides, nitrides and borides of at least one element selected from the group consisting of tungsten, molybdenum, chromium, tantalum, niobium, vanadium, titanium, zirconium 'and boron,`

and a powdery cementing metal of lower melting point than said particles, said cementing metal always including an appreciable amount of iron group metal, comprising the steps of continuous- 1y feeding a completed first type layer under means for depositing thereon a layer of an initial mixture for said second type layer and depositing said second type layer on said completed rst type layer, feeding said layers into means for compacting said -deposited layer-upon said first typelayer, feeding thereafter. said layers into a heating device for finally sintering said second type layer upon said rst type layer, and surbjecting thereafter the continuously fedrforward and united layers to a heat treatment according to a predetermined temperature-time curvein order to impart 'desired properties at least to said first type layer.

l5. A process of manufacturing a, layered armor composed of a number,` two as a. minimum, of layers or strata of different type material, a

first type being ferrous, tough and hard and inhard metal composition obtained by sintering ati initial ymixture of hard particles selected from carbides, nitrides, and borides of at least one element selected from the group consisting of tungsten, molybdenum, chromium, tantalum, niobium, vanadium, titanium, zirconium and boron, and a powdery cernenting metal of lower melting point than said particles, said cementing metal always including an appreciable amount. of iron group metal, comprising the steps of continuously feeding a completed first type layer under means for depositing thereon a layer of an initial mixture for said second type layer and depositing said second type layer on said completed first type layer, feeding said layers into means for compacting said deposited layer upon said first type layer, feeding subsequently said layers into a heating device for finally sintering said second Atype layer upon said first Atype layer, and subjecting thereafter the continuously fed forward,

united and still hot layers to further shaping at temperatures between about 450 C. to below 900 C.

. PAUL SCHWARZKOPF. 

